Negative results for ketamine use in severe acute bronchospasm: a randomised controlled trial

Background
Ketamine has bronchodilation properties. The aim of the single-centre, evaluator-blinded, randomised clinical trial study was to evaluate whether continuous infusion of ketamine is associated with improvement in respiratory mechanics correlated with bronchospasm relief, as compared with continuous infusion of fentanyl.

Methods
Adult patients submitted to invasive mechanical ventilation were included if they had an acute severe bronchospasm, due to status asthmaticus or COPD exacerbation. They were randomised to ketamine or a standard IV analgesia with fentanyl, both in bolus and continuous infusion. Measurements of respiratory mechanics (airway resistance – R_smax, dynamic compliance – C_dyn and intrinsic PEEP – PEEPi) both at baseline and 3 and 24 h after randomisation were performed. The main outcome of this study was to evaluate the improvement of R_smax in 3 h of continuous infusion of the study drugs.

Results
Ketamine use was not associated with greater reduction in R_smax when compared with fentanyl, either after 3 h (0 cm H₂O L–1 s–1 ± 6 vs. –3 cm H₂O L–1 s–1 ± 7.7, respectively; P = 0.16) or after 24 h (–3 cm H₂O L–1 s–1 ± 17 vs. –3.5 cm H₂O L–1 s–1 ± 13.7, respectively; P = 0.73). Patients randomized to the ketamine group did not have better improvements in delta PEEPi as compared with fentanyl in 3 h (P = 0.77) or in 24 h (P = 0.72).

Conclusions
In this study, ketamine use was not associated with improvement in ventilatory variables associated with bronchospasm.